1. Field of the Invention
Embodiments of the present invention relate to new methods for grafting of complex polymer coatings onto or from a surface of a substrate including surfaces of conductive and non-conductive materials.
More specifically, embodiments of the present invention relate methods for grafting of complex polymer coatings onto or from a surface of a substrate including surfaces of conductive and non-conductive materials, where the methods involve a new and convenient approach for the preparation of polymer coatings by electrochemically grafting designed reactive initiators or monomers onto the surface that are capable of polymerizing monomers, macromonomers, or crosslinking to themselves, or reacting with preformed polymers or mixtures or combinations thereof.
2. Description of the Related Art
Surface modifications and thin film coatings can be formed by attaching polymers via covalent end-group, forming polymer structures on the surface such as so-called “polymer brushes” on surfaces. This process, unlike non-covalent attachment, enhances the stability and durability of the films against solvent and other displacing agents such as surfactants. One known method for making polymer brushes involves the chemisorption of pre-formed polymers containing for example a polysiloxane backbone with grafted side chains having different exposed functional anchoring groups. However, this methodology require extensive synthetic efforts for the preparation of the functionalized polymers prior to reacting them with a surface.
Another method for making polymer brushes includes covalently attaching polymers onto SiO2 surfaces by ultra violet (UV) irradiation. For example, exposed benzophenone moieties on the outer layer can undergo photo induced cross-linking with other polymers. The benzophenone moiety is well known for its photo reactivity and its ability to attach to C—H bonds in a wide range of different chemical environments. However, most of such studies using this approach have been limited to the self-assembly of silanized benzophenone units, which can only be attached onto SiO2 surfaces or other oxide surfaces, but not electrodeposited on metallic electrode surfaces.
Other molecules including polymers can be electro-deposited on a wide variety of electrode materials such as platinum, gold, glassy carbon, ITO-covered surfaces and carbon felt. A number of monomers have been electropolymerized by cathodic and anodic polymerization, giving both electrically insulating and conducting polymer coatings, respectively. Previous methods include the electropolymerization of monomers such as pyrrole and indole derivatives to graft benzophenone onto surfaces with the purpose of photochemically immobilizing enzymes. Most known conducting polymers are prepared by oxidative electropolymerization (anodic). Most known insulating polymers are prepared by reductive electropolymerization (cathodic).
Prior art teaches methods for preparing polymer thin film coatings onto a solid surface by physical adsorption or chemical adsorption techniques. Most common film coatings are prepared by physical adsorption, such as dip-coating, drop casting, spin-coating, doctor blade film application, or roll-to-roll coating. The limitations of physical adsorption are that solvent, temperature, or mechanical abrasion can easily detach these coatings from the solid-substrate surface.
An approach for the preparation of polymer thin film coatings is to use chemical adsorption by attaching polymers via the formation of covalent bonds through a chemical reaction. One known method for forming robust polymer coatings consists in reacting the end-group of a pre-formed polymer (such as a macromolecule) to form so-called “polymer brushes”. This process, unlike non-covalent attachment, enhances the stability and durability of the films against solvent and other displacing agents such as surfactants. The reactive groups are chemically complementary to the surface to which the polymer is to be attached to. The types of chemistry involved for covalent attachment include acid-base chemistry, the attachment of thiols on noble metals, the attachment of silane on silica or hydroxyl surfaces, the reaction of an aldehyde with an amine, and other common organic reactions or metal-ligand chemistries. One known method for making polymer brushes involves the chemisorption of pre-formed polymers containing for example a polystyrene chain with an exposed functional reactive end-group such as a thiol group attached to a gold surface. An alternative is to use polymers with reactive side groups or hyperbranched macromolecules such as dendrimers having reactive peripheral groups on the surface. However, such process requires extensive synthetic efforts for the preparation of the functionalized polymers and is not readily applicable to conducting electrode substrates.
A favored method for preparing polymer thin film coatings is to directly electro-deposit polymers on a wide variety of electrode materials such as platinum, gold, glassy carbon, ITO-covered surfaces, and carbon felt. A number of monomers have been electropolymerized by cathodic and anodic polymerization, giving both electrically insulating and conducting coatings, respectively.
The study of the chemistry and biological applications of polymers such as polyethyleneglycol (PEG) is of immense interest both for fundamental and pharmaceutical applications. Traditionally, PEG has been used in biological research as precipitating agents for protein and other biological macromolecules and viruses, PEGylation of drugs for improving efficacy, and to facilitate biological cell fusion, a technique commonly used in cell hybridization technology. There is a growing interest for surface modification with PEG that offer new chemistries and application of surface analytical methods.
While numerous methods have been presented for preparing polymeric coating such as polymer brush coating on surfaces, many of these methods are restricted in use to certain type of surfaces. Thus, there is a need in the art for more robust methodologies and compositions for efficient coating of surfaces.